The present invention relates generally to power driving mechanisms, and more particularly to apparatus utilizing a vibratory member for driving tools or other members of various types into earth, coal, wood, concrete, asphalt, or other materials or substances.
In my application, Ser. No. 973,161, filed on even date herewith, is described tool driving apparatus in which one extremity of a resonant beam is mounted adjacent to a tool in the form of a cutter blade. A sonic generator is mounted on a tool holder or carrier that is driven by a continuous unidirectional force. The sonic generator is coupled to the other extremity of the resonant beam to set up resonant vibration therein. The tool is advanced intermittently along a work path responsive to the continuous unidirectional force exerted by the carrier and the force exerted by the sonic generator. To prevent destruction of the tool driving apparatus when the tool encounters an immovable object, i.e., an object that the oscillator force is unable to overcome, a protective gap is held between the neutral output position of the resonant beam and the tool. Specifically, the force of the sonic generator is sufficiently large relative to the unidirectional force to overcome the latter, and to drive the tool holder back away from the tool when the tool is unable to advance along the work path, thereby establishing the protective gap.